Diseased or otherwise deficient heart valves can be repaired or replaced with an implanted prosthetic heart valve. The terms “repair” and “replace” are used interchangeably throughout the specification, and a reference to “repair” of a defective native heart valve is inclusive of a prosthetic heart valve that renders the native leaflets non-functional, or that leaves the native leaflets intact and functional. Conventionally, heart valve replacement surgery is an open-heart procedure conducted under general anesthesia, during which the heart is stopped and blood flow is controlled by a heart-lung bypass machine. Traditional open surgery inflicts significant patient trauma and discomfort, and exposes the patient to a number of potential risks, such as infection, stroke, renal failure, and adverse effects associated with the use of the heart-lung bypass machine, for example.
Due to the drawbacks of open-heart surgical procedures, there has been an increased interest in minimally invasive and percutaneous replacement of cardiac valves. With percutaneous transcatheter (or transluminal) techniques, a valve prosthesis is compacted for delivery in a catheter and then advanced, for example, through an opening in the femoral artery and through the descending aorta to the heart, where the prosthesis is then deployed in the annulus of the valve to be restored (e.g., the aortic valve annulus). Although transcatheter techniques have attained widespread acceptance with respect to the delivery of conventional stents to restore vessel patency, only mixed results have been realized with percutaneous delivery of the more complex prosthetic heart valve.
Various types and configurations of prosthetic heart valves are available or have been proposed for percutaneous transcatheter valve replacement procedures. In general, prosthetic heart valve designs attempt to replicate the functions of the native heart valve being replaced and thus will include valve leaflet-like structures mounted in some manner within an expandable stent frame, which in some instances is made of a shape memory material and construction. With such shape memory or self-expanding stent frames, the prosthetic heart valve is crimped to a desired size and held in a compressed delivery configuration within a retaining sheath, sleeve or capsule of a delivery catheter, for example, for delivery to a treatment site within the heart. In certain percutaneous transcatheter valve replacement procedures, the delivery catheter is introduced into a vessel, for example, the femoral artery or the brachial artery and tracked through the vasculature to the heart. Once the delivery catheter and more particularly the prosthetic heart valve are properly positioned with the native valve to be replaced, the retaining sheath, sleeve or capsule is retracted from the prosthetic heart valve to permit the stent frame to return to its expanded diameter for implantation within the native valve.
A delivery catheter must often navigate through tortuous anatomy as it is tracked through the vasculature to the treatment site within the heart, to include traversing the aortic arch.
In order that the catheter may be navigated through various anatomical turns as it travels within the vasculature, including the sharp bend of the aortic arch, it is desirable that the clinician have the ability to accurately steer or deflect the catheter as it is guided and advanced to the treatment site. Typical mechanisms for catheter deflection employ a pull wire or wires connected to a distal portion of the catheter and controlled at a proximally located handle. With such mechanisms, when a wire is pulled, the catheter is deflected in the direction of the pulled wire. Although these pull wire mechanisms may work effectively, they add additional components and complexity to the catheter, as well as may increase an already comparatively large profile of a prosthetic heart valve delivery system. Accordingly, a need exists for improved steering mechanisms for a prosthetic heart valve delivery system that can accurately, safely, and successfully achieve deflection of a delivery catheter as it navigates the anatomy of the vasculature while advancing to a desired treatment site without adding additional components, complexity and/or profile to the catheter.